20.
Draw Lewis structures for each of
the following ions and indicate all
nonzero formal charges.
a)
CO
2- 3
b)
NH
1+ 4
c)
CHO
1- 2
d)
ClO
1- 2
21.
Draw Lewis structures for each of
the following ions and indicate all
nonzero formal charges.
a)
NO
1-^3
b)
NO
1+
c)
N
1- 3
d)
NO
1- 2
22.
For which molecules in Exercises 18
and 19 are more than one resonance
form important?
23.
For which ions in Exercises 20 and 21 are more than one resonance form important?
24.
Indicate all nonzero formal charge
on the resonance structures of
formaldehyde shown below and rank the structures in order of importance in describing the bonding. Explain your reasoning.
O C
HH
O C
HH
O C
HH
A B
C
25.
Which of the Lewis structures of fo
rmic acid shown below is preferred?
Justify your answer.
HOCOH
HC
O
OH
A^
B
26.
The hypochlorite ion, ClO
1-, is the active ingredient in bleach. Draw its
Lewis structure and determine the formal charges and oxidation states of both atoms. Hypochlorous acid is made by adding H
1+ to the hypochlorite
ion. Based on the formal charges, does hypochlorous acid have an H-Cl bond or an H-O bond?
27.
What are the formal charges and oxid
ation states of the nitrogen atoms in
N^2
O^4
?
N
O
N
O O
O
28.
Draw three resonance structures for the hyponitrite ion, N
O 2
2- 2
(one N-N
bond and two N-O bonds) and show all nonzero formal charges. Which structure is the preferred st
ructure? Justify your answer.
29.
List the following in order of increasing cabon-oxygen bond lengths and bond energies:
OC
O
OHC
O
H
CO
HC
H H
H O
A B C D
30.
List the following in order of increasing nitrogen-oxygen bond lengths and bond energies:
NO
1-, NO 3
1+, NOCl, NO
1- 2
31.
List the following in order of increasing nitrogen-nitrogen bond lengths and bond energies: N
H 2
, N 2
, N 2
H 2
. 4
32.
NO
has an odd number of electrons. Using only formal charge, rate the 2
three possible resonance structures below (1 = best, 3 = worst).
ONO
ONO
ONO
A
BC
The lone electron on two NO
molecules combines to form N 2
O 2
with the 4
Lewis structure shown in Exercise 27. Ba
sed on this fact where is the lone
electron on NO
? The difference is due to the 2
fact that the oxygen atom is
so electronegative that it takes the electrons it needs to fill its valence shell.
33.
Draw two structures for BF
, one that obeys the octet rule and one in which 3
boron is electron deficient. Based on
formal charge considerations, which
structure is preferred?
34.
Exercises 32 and 33 are examples of
exceptions to the octet rule. What
atom is the most common exception to the octet rule?
35.
Draw Lewis structures that show all nonzero formal charge for the three resonance forms of the cyanate ion (NCO
1-) and the fulminate ion (CNO
1-).
In each case, determine the resonance st
ructure that is most important in
describing the bonding in the ion. The cyanate ion is a stable ion, but the fulminate ion is used in explosives.
Suggest a reason fo
r this dramatic
difference in stability.
Chapter 5 The Covalent Bond
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